This just came up, I have an answer but I wanted to share it here...
"Is it possible to create an iris constraint based on cell_methods?"
I have a datafile which loads producing many cubes.
I would like to extract only those containing ensemble spread, which I can identify from their cell_methods, which are set to:
(CellMethod(method=u'standard_deviation', coord_names=(u'realization',), intervals=(), comments=()),)
Is there a way to filter the load so that I only read in the desired "ensemble spread" data ?